All posts tagged Insects

More than half a century ago, Karl von Frisch rocked the world of behavioral biology with his conclusion that the honeybees (Apis mellifera) can actually communicate the distance to and direction of valuable food sources through an elaborate “waggle dance.” In what later led to his receipt of the Nobel Prize in Physiology or Medicine, von Frisch determined that bees recruited by this dance used the information encoded in it to guide them directly to the remote location of the resource.

In the typical waggle dance, a foraging worker bee who has found by a rich food source returns to the hive, is greeted by other bees, and commences dancing on the vertical comb surface within the dark nest (in other species of bee, like Apis florea, the dance is performed on a horizontal surface in direct view of the sun and/or other landmarks). She dances in a figure-eight pattern, alternating “waggle runs,” during which she vigorously waggles her body from side to side in a pendulum motion at about 13 times per second as she moves forward in a straight line, with return phases in which she circles back to the approximate starting point of the previous waggle run, alternatingly between clockwise and counter-clockwise returns. Here’s a video of a bee doing the waggle dance:

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As the video indicates, the honeybee’s dance encodes key information about the resource. For instance, as she performs waggle runs on the vertical comb surface, her average body angle with respect to gravity corresponds to the direction of the food source relative to the current position of the sun (the sun’s azimuth). Accordingly, if the food source lies in the exact direction of the sun, she will waggle straight upwards; if the food lies, say, 30 degrees to the right of the imaginary line to the sun, she will angle upwards 30 degrees to the right of vertical. Also, the duration of her waggling runs is directly linked to the flight distance from the hive to the food source, with (for many bee subspecies) every extra 75 milliseconds of waggling adding roughly another 100 meters to the distance. Further, the more attractive the destination, the longer and more vigorously she dances, and the more quickly she returns for the start of each waggle run. Depending on the richness of the food source, she may perform up to 100 waggle runs in a single dance.

Next week ... the Tango!

Cognitive Complexity

It seems, then, that honeybees have evolved an extraordinary complex form of symbolic communication about distant resources, one that is beyond the capabilities of virtually every other species except for humans. Not bad for an insect.

The cognitive tasks implicated by the waggle dance are not insignificant: the dancer must remember the location and characteristics of a specific site she has seen on her foraging trips, and translate this information into the appropriate dance characteristics. She must also remember and take into account the position of the sun, and update that position as the sun moves (the ability to compensate for the sun’s movement by memory has been documented by researchers observing dances over several hours of overcast weather, when there are no celestial cues to be seen). The observing bees must “read” the dance, translate their sensory input into a resource location, and then find the resource, navigating as necessary around hills, houses and other obstacles.

In fact, the feat is so stunning that von Frisch’s findings were initially met with significant skepticism and controversy.1 At this point, the controversy has essentially been settled, with scientists recognizing that there is compelling evidence that honeybees really do communicate and act on the information encoded in the waggle dance, even though uncertainty remains regarding exactly which signals (tactile, odor, vibrations, air flows, etc.) the observing bees use to translate the dance into actionable information regarding the resource location.2

Is the Waggle Dance a “Language”?

So, the waggle dance is an extremely complex communication system, but is it a language?

Eileen Crist, Associate Professor in Science and Technology in Society at Virginia Tech, makes a rather compelling case that the waggle dance embodies many of the attributes of a true language.3 After noting that the waggle dance is always performed in front of an audience and is clearly communicative in nature, she describes some of the principal features that support its being characterized as a language:

Rule-Governed. If a communication system is to be considered linguistic in nature, it generally must be based on a set of rules that are structured and used with regularity. This is the case with the waggle dance: the dance is always performed in a designated place within the hive, it is never done unless an audience is present, and it always follows a standard template for conveying direction, distance, and desirability. While the general rule is that the waggle dance is to be used to inform other bees about sources of nectar, when the colony has a special requirement (e.g., locating water when the hive is overheating or finding a new home when part of the colony must relocate) then the rules dictate that the dance purpose switches to this pressing need. Also, the general rule is that foragers dance about rich, reliable and near resources, but in times of need the “dance threshold” for less desirable resources is lowered.

Complexity. A key dimension of a true language is its complexity, as it is unlikely that a communication system based on just a few rules will qualify as a language. The bee dance rules are not only extremely intricate, but they are applied in a versatile and complex fashion to respond to differing environmental factors and hive requirements.

Stability and Dynamism. A core feature of human language is that a relatively fixed and stable syntax enables the dynamic generation of an indefinite number of new sentences. Similarly, while the waggle dance always takes the same recognizable forms, it “accommodates different purposes, shifting circumstances, urgent needs, and unprecedented events; while structurally identical every time, it is also contextually flexible.”

Symbolic. By itself, the symbolic nature of the waggle dance has led to its being called a language. The dance symbolically represents conditions existing in the real world, actually enabling human researchers to “read” the information encoded in the dance to find specific honeybee food sources and even to design experiments about honeybee foraging behavior.

Performative. According to linguistic theory and as first articulated by John Austin, languages not only describe the world, they also include what he called “performative” utterances, which are used to carry out actions.4 Not only is the waggle dance symbolically descriptive, but it has performative force in the sense that it elicits action from the bees who watch it (as Crist notes, the performative nature of the waggle dance is implicit in the way in which scientists “routinely deploy a vocabulary of announcing, reporting, summoning, recruiting, soliciting, inviting, commanding, and guiding” in describing it).

James Gould, Professor of Ecology and Evolutionary Biology at Princeton University, summarized both the controversy over the issue and the nature of honeybee dance communication as follows:

Some of the resistance to the idea that honey bees possess a symbolic language seems to have arisen from a conviction that “lower” animals, and insects in particular, are too small and phylogenetically remote to be capable of “complex” behavior. There is perhaps a feeling of incongruity in that the honey bee language is symbolic and abstract, and, in terms of information capacity at least, second only to human language.5

Gould estimates that the waggle dance is capable of communicating at least 40 million unique messages (“sentences”), more than 10 times as many as any other animal except for man.6

Not surprisingly, not everyone agrees that the waggle dance constitutes a true language. For example, Stephen Anderson, Professor of Linguistics at Yale University, acknowledges that honeybee dance communication is elaborate and cognitively rich, but concludes that it is unlike human natural language in that, for example, it is genetically fixed rather than learned through environmental interactions, it lacks a syntax in which the order of the communicative elements (words or actions) impacts meaning, and there is a close correspondence between the structure of the dance signals and the nature information to be conveyed (e.g., orientation of the waggle run and the direction to the resource).7

Some bees are better at the dance than others...

To Bee or Not to Bee

In the end, there will probably always be debate and disagreement over whether the waggle dance is a true language. Clearly, the waggle dance and human language are vastly different communication systems, and how we label the waggle dance in human terms may be missing the point. From the honeybee standpoint, the dance serves its purposes and contains all of the communicative nuances that the bees need within their environment. Maybe, the real point is that we should sit back and appreciate the fact that the honeybee, a small insect with tiny brain, has been able to evolve a system of communications that is so sophisticated that it has challenged human linguists to wrestle with the question of what distinguishes a true language and whether human language is really so unique.

What was all the fanfare about? Are we about to enter a new era in which paparazzi stalk bees rather than reality TV stars? (We won’t complain if this is the case.) PhysOrg.com4 summarized the context as follows:

Scientists at Queen Mary, University of London and Royal Holloway, University of London have discovered that bees learn to fly the shortest possible route between flowers even if they discover the flowers in a different order. Bees are effectively solving the ‘Travelling Salesman Problem’, and these are the first animals found to do this.

The Travelling Salesman must find the shortest route that allows him to visit all locations on his route. Computers solve it by comparing the length of all possible routes and choosing the shortest. However, bees solve it without computer assistance using a brain the size of grass seed.

Professor Lars Chittka from Queen Mary’s School of Biological and Chemical Sciences said: “In nature, bees have to link hundreds of flowers in a way that minimises travel distance, and then reliably find their way home – not a trivial feat if you have a brain the size of a pinhead! Indeed such travelling salesmen problems keep supercomputers busy for days. Studying how bee brains solve such challenging tasks might allow us to identify the minimal neural circuitry required for complex problem solving.”

In actuality, the bumblebees’ achievements, while impressive, were a bit more modest than publicized.

Bumblebees (Bombus terrestris) do indeed visit flowers in predictable sequences called “traplines,” and the UK research team wanted to learn more about whether these sequences simply reflect the order in which flowers are discovered or whether they result from more complex navigational strategies enabling bees to optimize their foraging routes. Accordingly, the researchers set up an array consisting of four (not hundreds of) artificial flowers, which they introduced to bumblebees in sequence.

The researchers observed that over time the bees tended to stop visiting the artificial flowers in their discovery order and, through a process of trial and error, began reorganizing their preferred routes to minimize total flight distance. In general, the bumblebees adopted a primary route and two or three less frequently used secondary routes, with the primary route typically being the shortest distance route. The bees also did a (reasonably) good job of remembering the most efficient route after an overnight break.

Even though the bees gravitated toward the shortest route, they did continue to experiment with novel routes, a behavior that – the researchers hypothesized – might allow them to fine tune their behavior as new sources of food were found over time.

Now, in their research paper5, the UK team did note that the bees’ search to find the shortest path among flowers is analogous to the traveling salesman problem, and did state that “Our findings suggest that traplining animals can find (or approach) optimal solutions to dynamic traveling salesman problems (variations of the classic problem where availability of sites changes over time) simply by adjusting their routes by trial and error in response to environmental changes.” These observations are, however, just a tad less dramatic than the “triumph over supercomputers” celebrated in the popular media reports on the research.

So what are the morals of this story?

While all too often animals are derided as “dumb beasts” and the like, sometimes we go in the opposite direction, overstating what animals are capable of accomplishing in order to create a sensation.

Even without the hyperbole, bumblebee route optimization behavior is noteworthy. There are often multiple ways to solve difficult problems, and sometimes the efficient approaches developed by animals who do not boast large brains can be surprisingly effective.

Insects, both in collective groups and as individuals, seem to be particularly adept at finding rational solutions that have an almost mathematical feel to them.

In a recent post I described how pigeons are better than humans at solving the Monty Hall problem and might therefore prove to be formidable competitors on Let’s Make a Deal. In this post, I have some good news and some bad news for those of you readers who are human (I make no assumptions in this blog). The good news is that I have yet to see any research showing that pigeons can triumph over humans at Jeopardy. The bad news is that the top two winners on Let’s Make a Deal could well end up being a pigeon and an ant, leaving the human contestants to go home with nothing more than an electronic version of the game (and perhaps a goat or two).

Consider the following scenario: You want to buy a house with a big kitchen and a big yard, but there are only two homes on the market–one with a big kitchen and a small yard and the other with a small kitchen and a big yard. Studies show you’d be about 50% likely to choose either house–and either one would be a rational choice. But now, a new home comes on the market, this one with a large kitchen and no yard. This time, studies show, you’ll make an irrational decision: Even though nothing has changed with the first two houses, you’ll now favor the house with the big kitchen and small yard over the one with the small kitchen and big yard. Overall, scientists have found, people and other animals will often change their original preferences when presented with a third choice.

Not so with ants. These insects also shop for homes but not quite in the way that humans do. Solitary worker ants spread out, looking for two main features: a small entrance and a dark cavity. If an ant finds an outstanding hole–such as the inside of an acorn or a rock crevice–it recruits another scout to check it out. As more scouts like the site, the number of workers in the new hole grows. Once the crowd reaches a critical mass, the ants race back to the old nest and start carrying the queen and larvae to move the entire colony.

The article goes on to describe some research on ant decision-making conducted by Stephen Pratt, an Arizona State University behavioral ecologist, and Susan Edwards, of the Department of Ecology and Evolutionary Biology at Princeton University. In this research, published in Proceedings of the Royal Society: Biological Sciences2, Pratt and Edwards designed a series of possible nests for 26 ant colonies:

The duo cut rectangular holes in balsa wood and covered them with glass microscope slides. The researchers then drilled holes of various sizes into the glass slides and slipped plastic light filters under the glass to vary the features ants care about most. At first, the colonies only had two options, A and B. A was dark but had a large opening, whereas B was bright with a small opening. As with humans, the ants preferred both options equally: The researchers found no difference between the number of colonies that picked A versus B.

Then the scientists added a third option, called a decoy, that was similar to either A or B in one characteristic but clearly worse than both in the other (a very bright nest with a small opening, for example). Unlike humans, the ants were not tricked by the decoy, the team reports online today in the Proceedings of the Royal Society B. Although a few colonies picked the third nest, the other colonies did not start favoring A or B and still split evenly between the two.

Ants can make better decisions because they take advantage of collective wisdom and do not “overthink” their options the way humans are prone to do. As Pratt noted in an article published in PhysOrg.com3, “Typically we think having many individual options, strategies and approaches are beneficial, but irrational errors are more likely to arise when individuals make direct comparisons among options.”

This research is particularly fascinating in that it poses a direct challenge to our core belief that we will always enjoy a large advantage over other animals when there is an intellectual way to solve a problem: sure, animals may have highly-evolved senses of smell, they may be fast, they may have impressive reflexes and their instincts may be powerful, but where we humans are able to harness our large brains, we will inevitably prevail.

In fact, though, we should hold off before patting ourselves on the back. As this (and other) research shows, we suffer from biases and flaws in the way we approach thought problems that can lead to irrational decisions and that can even put us at a disadvantage vis-à-vis other animals, including the birds and the ants.

News flash: this month Current Biology1 reported that that stressed bees have lower levels of neurotransmitters such as dopamine and serotonin and exhibit pessimism, a cognitive trait supposedly limited to “higher” animals.

Ok, this is waaay cool! Who knew that bees could be pessimists or even that they have “human” neurotransmitters like dopamine and serotonin coursing through their little systems?

ScienceDaily2 provided a layperson’s description of the research, reporting:

To find out how bees view the world, the researchers set them up to make a decision about whether an unfamiliar scent portended good or bad things. First, the bees were trained to connect one odor with a sweet reward and another with the bitter taste of quinine. The bees learned the difference between the odors and became more likely to extend their mouthparts to the odor predicting sugar than the one predicting quinine.

Next, the researchers divided the bees into two groups. One group was shaken violently for one minute to simulate an assault on the hive by a predator such as a honey badger. The other group was left undisturbed. Those bees were then presented with the familiar odors and some new ones created from mixes of the two.

Agitated bees were less likely than the controls to extend their mouthparts to the odor predicting quinine and similar novel odors, the researchers found. In other words, the agitated bees behaved as if they had an increased expectation of a bitter taste, the researchers said, demonstrating a type of pessimistic judgment of the world known as a “cognitive bias.”

Now, I don’t approve of shaking bees (violently or otherwise), even in the interest of scientific advancement. How would the researchers feel if giant swarms of bees swooped down on them and their families to see whether being blanketed by carpets of buzzing insects triggered negative emotional responses in humans?

Nevertheless, this study is an amazing demonstration of the deep commonality we share with our animal brethren (and sistren). The notion that humankind and beekind share the same neurotransmitters and similar stress reactions is somehow strangely comforting – c’mon, insects, we’re all in this thing together – we can do it! It’s almost enough to make you want to go out and hug a bee.